Concrete Workability, Setting and Manufactoring.pptx

Contents
1)Factors affecting Concrete Workability

2)Setting of Concrete

3)Factors affecting Setting

4)Manufacturing of Concrete

5)Various stages of manufacture of concrete (Batching, Mixing, Transporting ,Placing ,Compacting ,Curing ,Finishing. )

1. Advance Concrete Technology

2. Group Members Name Registration Number Muhammad Bilal 16PWCIV4617 Tauseef Ahmad 16PWCIV4566 Jawad Hussain 15PWCIV4465 Farhad Hamid 2015/CUP/CIV-1429

3. Contents Factors affecting Concrete W orkability Setting of Concrete Factors affecting Setting Manufacturing of Concrete Various stages of manufacture of concrete (Batching, Mixing, Transporting ,Placing ,Compacting ,Curing ,Finishing. )

4. Factors affecting Concrete W orkability

5. 1. Water content or Water Cement Ratio More the water cement ratio more will be workability of concrete High water content results in a higher fluidity and greater workability but reduces the strength of concrete Increased water content also results in bleeding , hence, increased water content can also mean that cement slurry will escape through the joints of the formwork (Shuttering)

6. W/C ratio Vs Workability Graphically

7. Type of aggregate vs Workability

8. 2. Amount and type of Aggregate L arger Aggregate sizes have relatively smaller surface areas (for the cement paste to coat) and since less water is required for it so it results in greater workability and vice versa. Greater size of Aggregate- less water is required to lubricate it, the extra water is available for workability. Using smooth and round aggregate increases the workability. Workability reduces if angular and rough aggregate is used. Porous aggregates require more water compared to non absorbent aggregates for achieving same degree of workability

9. 3. Aggregate Cement Ratio More the ratio less the workability. Since less cement mean less water, so the paste is stiff.

10. 4. Weather Conditions (a) Temperature - If temperature is high, evaporation increases, thus workability decreases. (b) Wind - If wind is moving with greater velocity, the rate of evaporation also increase reduces the amount of water and ultimately reducing workability. c) Relative Humidity

11. 5. Admixtures Chemical admixtures can be used to increase workability. Use of air entraining agent produces air bubbles which acts as a sort of ball bearing between particles and increases mobility, workability and decreases bleeding. The use of fine pozzolanic materials also has better lubricating effect and more workability.

12. 6 . Sand to Aggregate ratio If the amount of sand is more the workability will reduce because sand has more surface area and more contact area causing more resistance.

13. Setting of Concrete The transition process of changing of concrete from plastic state to hardened state is setting OR The hardening of concrete before it gains strength. Setting of concrete is based or related to the setting of cement paste Thus cement properties greatly affect the setting time .

14. Factors affecting Setting

15. Batching and Mixing of Concrete Jawad Hussain ( 15PWCIV4465)

16. BATCHING OF CONCRETE It is the process of measurement of different ingredients(Coarse aggregates, fine aggregates, cement etc ) of concrete into specified proportions. Types of Batching process Batching by volume Batching by weight

17. BATCHING OF CONCRETE BATCHING BY VOLUME: Volumetric batching of concrete is a method used to measure materials by volume rather than weight to produce concrete. In this process, the components of concrete - cement, aggregates, and water - are measured by volume rather than weight. This method can be particularly useful in situations where the availability of precise weighing equipment is limited or where batching by weight is not practical.

18. BATCHING OF CONCRETE BATCHING BY WEIGHT: In this method, the components of concrete - cement, aggregates, and water - are measured by weight. Batching by weight offers greater precision and control over the mix proportions compared to volumetric batching, making it suitable for projects that require consistent and precise concrete mixes.

19. COMPONENTS OF BATCHING PLANT A batching plant, also known as a concrete batching plant or concrete mixing plant, is a facility where various ingredients are combined to produce concrete. The primary components of a typical batching plant include: Aggregate Bins : These are storage containers for different types of aggregates, such as sand, gravel, or crushed stone. The aggregates are stored separately and then fed into the mixing process as needed. Weighing System : Batching plants are equipped with weighing systems to measure the quantities of cement, aggregates, and sometimes other materials accurately. These systems typically include load cells and scales to ensure precise measurements. Cement Silos : Cement silos are storage containers for cement powder. They are designed to store large quantities of cement and often feature mechanisms for accurate metering and dispensing of the cement into the mixing process. Water Storage and Metering : Batching plants have facilities for storing and metering water, which is a crucial component of concrete production. Water is typically measured and added to the mixing process in controlled amounts to achieve the desired consistency and workability of the concrete.

20. COMPONENTS OF BATCHING PLANT Mixing Unit : The mixing unit is where the various ingredients are combined to produce concrete. It usually consists of a mixer, which thoroughly blends the cement, aggregates, water, and any additives or admixtures to form a homogeneous mixture. Control System : Batching plants are equipped with control systems that oversee and regulate the entire mixing process. These systems can be manual, semi-automatic, or fully automatic, depending on the level of automation and control desired. They allow operators to monitor parameters such as material quantities, mixing times, and discharge rates, ensuring consistent and accurate production of concrete. Batching Plant Structure : The batching plant is housed within a structure that provides shelter and support for the various components. This structure may include platforms, catwalks, and access stairs for maintenance and operation. Auxiliary Equipment : Depending on the specific requirements of the batching plant and the type of concrete being produced, additional auxiliary equipment may be included. This can include conveyors for transferring materials, storage tanks for admixtures, and heating or cooling systems for controlling the temperature of the concrete mix.

21. CONCRETE BATCHING PLANT

22. MIXING OF CONCRETE The mixing of concrete is a critical step in the production process, where various ingredients are combined to form a homogeneous mixture that will ultimately harden into a strong and durable material. Proper mixing ensures that the concrete has the desired properties, including strength, workability, durability, and uniformity.

23. TYPES OF MIXING OF CONCRETE Hand Mixing : This method involves manually mixing the concrete ingredients using shovels, hoes, or other hand tools. It is typically used for small-scale projects or in situations where access to mechanical mixers is limited. While hand mixing is labor-intensive and less efficient than mechanical methods, it can be suitable for small batches or on-site repairs.

24. TYPES OF MIXING OF CONCRETE Machine Mixing : Continuous Mixers : Continuous mixers are used in larger concrete plants and are capable of producing a continuous flow of concrete. They typically feature rotating blades or paddles that continuously mix the ingredients as they are fed into the mixer. Batch Mixers : Batch mixers are commonly used in concrete plants and construction sites. They mix the ingredients together in batches.

25. TYPES OF BATCH MIXERS Tilting Drum Mixers : Tilting drum mixers have a rotating drum that tilts to one side to discharge the concrete. They are commonly used in small to medium-sized concrete plants and construction sites. Tilting drum mixers are versatile and can handle a wide range of concrete mixes. Tilting drum mixers consist of a cylindrical drum mounted on a horizontal axis. The drum is open at the top and has blades or paddles inside for mixing. The drum is supported by a frame or chassis, and it can tilt forward or backward to charge and discharge the ingredients.

26. MIXING AND DISCHARGING OF TILTING DRUM MIXER Mixing : Once the ingredients are loaded, the drum is tilted back into the mixing position, and it begins to rotate. The rotation of the drum causes the blades or paddles inside to mix the ingredients thoroughly, ensuring a homogenous mixture. Discharging : After the mixing is complete, the drum is tilted forward again to discharge the mixed concrete. The discharge chute or opening at the bottom of the drum allows the concrete to be poured out.

27. TYPES OF BATCH MIXERS Non-Tilting Drum Mixers : Non-tilting drum mixers have a rotating drum that does not tilt for discharge. Instead, the concrete is discharged through a chute at the bottom of the drum. Non-tilting drum mixers are often used for larger batches and higher production rates.

28. TYPES OF BATCH MIXERS Reversing drum mixer (truck mixer) - The reversible drum mixer is similar to the non tilting mixer except that the same opening is used to add the constituents and to discharge the aggregate. The drum of the reversing drum mixer rotates in one direction to mix the ingredients thoroughly. Once the mixing is complete, the direction of rotation is reversed, causing the drum to tilt in the opposite direction.

29. TYPES OF REVERSING TRUCK MIXERS REAR DISCHARGE TRUCKS Rear discharge trucks require both a driver and a "chute man" to guide the truck and chute back and forth to place concrete in the manner suitable to the contractor.

30. TYPES OF REVERSING TRUCK MIXERS Advantages : Accessibility: Rear discharge truck mixers provide easy access to the drum for loading and cleaning, reducing downtime between batches. Maneuverability : The rear discharge design allows for precise placement of concrete in tight or congested construction sites. Operator Safety: Operators have better visibility and control over the discharge process from the rear of the truck.

31. TYPES OF REVERSING TRUCK MIXERS Front discharge trucks - Newer front discharge trucks have controls inside the cab of the truck to allow the driver to move the chute in all directions. Advantages : Enhanced Visibility: Operators have better visibility of the discharge process from the front of the truck, allowing for improved maneuverability and control during concrete placement. Accessibility: Front discharge trucks provide easy access to the drum for loading and cleaning, reducing downtime between batches. Precise Placement: The front discharge design allows for precise placement of concrete in various construction scenarios, such as pouring into forms or structures with limited access.

32. TYPE OF BATCH MIXER Pan Mixer A pan type mixer is a forced–action mixer, as distinct from drum mixer which relies on the free fall of the concrete inside the drum. The pan mixer consist of a circular pan rotating about its Axis with one or two stars paddles rotating about vertical axis of pan. Components of a pan mixer are: Pan Shaft Scraper

33. Transporting and Placing of Concrete Farhad Hamid ( 2015/CUP/CIV-1429)

34. Methods of Concrete Transportation Concrete Mix Transportation Defined as the process of transferring concrete from the mixing plant to the construction site . Main Objective To maintain the intended water-cement ratio, consistency, air content, and homogeneity of the concrete mix during transportation

35. Important Factors in Choosing Transportation Prevent Segregation Ensure that the mix does not change its state as specified in the contract. Maintain Workability Do not reduce the workability of the mix during transportation. Efficient Organization Plan and execute the transportation process in a well-thought-out and efficient manner.

36. Timely Delivery Deliver the concrete within the acceptable time limits to prevent delays and honeycombing. Consider Factors Take into consideration factors like mix type, construction size, weather conditions, and cost when choosing the mode of transport. Avoid Segregation Choose the appropriate mode of transportation to prevent segregation and maintain the quality of the concrete .

37. Categories of Transportation Mortar Pan It is a labor intensive method and generally used for small works. There are no chances of segregation of concrete. In hot weather, there is a substantial loss of water b) Wheelbarrow or Hand cart It is normally used on ground level i.e. road construction and other similar structures. Segregation can occur if transportation is done on rough roads, however this problem can be minimized if pneumatic tyres are used

38. c) Belt Conveyor Has limited application due to chances of segregation on steep slopes, roller points, and changes in direction of the belt. It also involves over exposure of concrete to the environment . d) Concrete Pump Pumping is the most sophisticated method for concrete transportation . It's perfect for limited spaces or large quantities.

39. e) Transit Mixer Popular equipment for transporting concrete over a long distance, especially in ready mix concrete plants. They are truck-mounted with a capacity of 4 to 7 cubic meters

40. Concrete Placing Placing Program Before any concrete is placed, a detailed plan is made for equipment, layout, procedures, and methods. Formwork Inspection No concrete is placed until the formwork is inspected and deemed suitable for placement. Continuous Flow Equipment for conveying concrete should ensure a practically continuous flow of concrete during depositing, without segregation of materials

41. Direct Placement Concrete is placed directly in its final position without re handling or causing segregation. Confinement In locations where direct placement is not possible, suitable drop and Elephant Trunks are used to confine the movement of concrete. Special Care Concrete dropped from a height, especially if reinforcement is in the way, is handled with special care to avoid segregation.

42. Concrete Placement Techniques Concrete placement is a crucial step in construction, requiring careful planning and execution. Various techniques are employed to ensure the concrete is properly distributed and compacted, including pouring, pumping, and hand-placing. Each method has its own advantages and considerations for maximizing strength and quality. Proper concrete placement techniques are essential for achieving the desired structural integrity, surface finish, and long-term durability of the final product

43. Concrete Consolidation Proper consolidation of freshly placed concrete is crucial to remove air pockets and ensure a dense, uniform finish. This is typically done using vibrating equipment, such as internal vibrators or surface vibrators, to compact the concrete and eliminate voids.

44. Factors Affecting Concrete Placement Concrete Mixture Design The water-to cement ratio, aggregate gradation, and admixture content all influence the pumpability , flowability , and finishing characteristics of the concrete mix . Reinforcement Layout The presence and spacing of steel reinforcement can create obstacles for concrete placement, requiring careful planning and coordination to ensure complete encapsulation and proper consolidation.

45. Weather Condition s Temperature , humidity, and wind can significantly impact the workability and curing of freshly placed concrete. Monitoring these factors is crucial for optimal placement and strength development . Formwork Configuration The design and construction of formwork can impact the ease of concrete placement, particularly in areas with complex shapes or limited access. Proper formwork preparation is essential.

46. Safety Considerations in Concrete Placement Protective Equipment Ensure all workers wear hard hats, safety glasses, steel-toed boots, and high-visibility vests to prevent injuries during concrete placement Site Preparation Clearly mark hazards, install barricades, and establish designated work zones to minimize the risk of accidents and maintain a safe work environment Handling Precautions Train workers on proper techniques for lifting and moving heavy concrete buckets or hoses to prevent back injuries and other musculoskeletal issues .

47. Conclusion and Key Takeaways In conclusion, the transportation and placement of concrete require careful planning, specialized equipment, and attention to safety. Key takeaways include the diverse concrete delivery methods, the importance of concrete pumping systems, and best practices for consolidation and curing. By mastering these techniques, construction teams can ensure durable, high-quality concrete structures that stand the test of time.

48. Compaction, Curing and Finishing of Concrete Tauseef Ahmad (16PWCIV4566)

49. Compaction The process of removing entrapped air from concrete and making it dense is called compaction of concrete. If air is not removed, it leads to 1) Honeycombing 2) reduced strength

50. Compaction Contd… Experiments show that 1% air reduces the strength of concrete by 6%. Q: Why compaction is important? Air voids reduces strength Air voids increases permeability Air voids reduces durability Due to air voids, moisture and air penetrates into concrete leads to rusting of reinforcement

51. Compaction Contd… There are 2 methods of compaction: Hand compaction Mechanical compaction Hand Compaction : Done for ordinary and unimportant structures. Can be further divided into 3 methods. a) Rodding: The rodding method of compaction is manual technique used to compact concrete in small molds or forms, typically for laboratory specimens or small-scale construction projects. The rod having length of 2m, diameter of 16mm is used.

52. Compaction Contd… Rodding: The rodding method of compaction is manual technique used to compact concrete in small molds or forms, typically for laboratory specimens or small-scale construction projects. The rod having length of 2m, diameter of 16mm is used.

53. Compaction Contd… b) Ramming: This method is used to compact PCC on ground. It is not used for RCC. c) Tamping: The compaction is done by beating or applying pressure on the surface of concrete. Tamping tool is used having cross-section of 10x10 cm.

54. Compaction Contd… 2) Mechanical Compaction : In this method vibration is imparted to concrete by mechanical means. Due to this vibration air bubbles comes to the top and is eventually expelled. This can be of various types. a) Internal Vibration: Most common technique of compacting concrete and results in high quality concrete. A poker or needle is used, inserted inside concrete, having diameter of 20 to 75mm and length of 25 to 90cm. Frequency range is 3500 to 5000 rpm .

55. Compaction Contd… a) Internal Vibration: Most common technique of compacting concrete and results in high quality concrete. A poker or needle is used, inserted inside concrete, having diameter of 20 to 75mm and length of 25 to 90cm. Frequency range is 3500 to 5000 rpm. Effective method of compaction as energy is uniformly distributed.

56. Compaction Contd… b) External Vibration: This refers to the process of compacting concrete using vibration applied externally to the formwork or surface of concrete. It is used where Internal Vibration cannot be used like in thin sections, heavy reinforcement. Less effective Consumes more power Requires strong formwork

57. Compaction Contd… c) Table Vibration: used to compact concrete in laboratory. d) Platform Vibration: similar to table vibration but on large scale

58. Compaction Contd… e) Surface Vibration: also known as vibrating screeds, is a method used to compact and level the surface of freshly poured concrete. Not effective beyond 15cm depth.

59. Curing It is a process of maintaining adequate moisture and temperature conditions, to allow concrete to properly hydrate and develop strength. Once concrete has been placed and compacted it must be allowed to cure properly to develop good final properties. Strength of concrete comes from hydration of cement. To cure properly, the cement paste must be fully saturated with water. .

60. Curing Contd… If hydration reaction stops, concrete strength development also get affected. Not keeping concrete surface moist will result in development of shrinkage cracks. Methods of Curing : Water is sprayed over the concrete Concrete is covered with plastic or damp fabric to stop evaporation

61. Curing Contd… Weather plays an important role in curing process. Hot windy weather, rapid evaporation, so frequency of curing required will be high. Cold weather, rate of evaporation slow, so frequency of curing required will be less.

62. Finishing Concrete that will be visible needs finishing. Screeding/strike off: Cutting off excess concrete to bring top surface to a proper grade.

63. Finishing Contd… Bull Float : After screeding floating is done. It eliminates high and low spots and furthers levels the surface of concrete.

64. Finishing Contd… Contraction joints : done with hand groover or by inserting strips of plastic/wood/metal etc into unhardened concrete.

65. Finishing Contd… If smooth, hard, dense surface is desired, floating should be followed by steel trowelling . If slip resistance surface is desired, brooming is done.